96 national geographic • March 2018
PHYLUM CHORDATA
DISTANT
COUSINS
It would be hard to find two animals as dissimilar
as the giraffe and an invertebrate sea squirt
such as Ciona savignyi, at right. And yet they
share a common Cambrian chordate ancestor.
While the giraffe extends the notion of spinal
column to the ultimate extreme, a sea squirt
possesses a central notochord only fleetingly, in
its larval stage. With its muscular tail, the larva
swims about for a few days until it finds
a suitable surface to attach to. Then it dissolves
and absorbs its own tail, and morphs into
a spineless, immobile adult.
GIRAFFE PHOTOGRAPHED AT SAFARI WEST